This invention relates generally to techniques for delivering radiofrequency (RF) energy for the ablation of cellular tissue and, more particularly, to techniques for delivering RF energy for the ablation of prostate tissue for the treatment of benign prosthetic hypertrophy or hyperplasia (BPH).
Benign prostatic hypertrophy or hyperplasia (BPH) is one of the most common medical problems experienced by men over 50 years old. Hyperplastic enlargement of the prostate gland often leads to compression of the urethra, resulting in obstruction of the urinary tract and the subsequent development of various symptoms, including frequent urination, a decrease in urinary flow, nocturia, pain, discomfort, and dribbling. The association of BPH with aging has been shown to exceed 50% in men over 50 years of age and increases in incidence to over 75% in men over 80 years of age. Symptoms of urinary tract obstruction occur most frequently between the ages of 65 and 70, when approximately 65% of men in this age group have prostatic enlargement.
At the present time, there is no proven effective nonsurgical method for the treatment of BPH and the current surgical procedures are not totally satisfactory. Patients suffering from the obstructive symptoms of this disease are provided with few options: cope with the symptoms (conservative management), submit to drug therapy at an early stage, or submit to one of the current surgical procedures. More than 30,000 patients per year undergo surgery in the United States for the removal of prostatic tissue. This represents less than five percent of the men exhibiting clinically significant symptoms.
Those suffering from BPH are often elderly men, many with additional health problems which increase the risks of surgical procedures. Surgical procedures for the removal of prostatic tissue are associated with a number of complications, including anesthesia associated morbidity, hemorrhage, coagulopathies, pulmonary emboli and electrolyte imbalances. These surgical procedures can also lead to cardiac complications, bladder perforation, incontinence, infection, urethral or bladder neck stricture, retention of prostatic chips, retrograde ejaculation, and infertility. Due to the extensive invasive nature of the current surgical procedures for obstructive uropathy, the majority of patients delay definitive treatment of BPH. This can lead to serious damage to structures secondary to the obstructive lesion in the prostate, such as bladder hypertrophy, hydronephrosis, and dilation of the kidney pelves. Furthermore, younger men suffering from BPH who wish to avoid risk complications, such as infertility, are often forced to avoid surgical intervention. Thus the need, importance and value of improved surgical and nonsurgical methods for treating BPH is unquestionable.
High-frequency currents are used in various electrocautery procedures for cutting human tissue, especially when a bloodless incision is desired or when the operating site is not accessible with a normal scalpel. In the latter instance, a thin instrument can be inserted through a natural body opening, such as the esophagus, intestine or urethra, for the removal of prostatic adenomas, bladder tumors or intestinal polyps. The high-frequency current is fed by a surgical probe into the tissue to be cut, causing boiling and vaporization of the cell fluid so that the cell walls rupture and the tissue is separated.
Ablation of cellular tissues in situ has been used in the treatment of many diseases and medical conditions either alone or as an adjunct to surgical removal procedures. It is often less traumatic than surgical procedures and may be the only alternative where other procedures are unsafe. Ablation devices have the advantage of using a destructive energy that is rapidly dissipated and reduced to a non-destructive level by conduction and convection forces of circulating fluids and other natural body processes.
Ablation devices typical utilize microwave, radiofrequency (RF), acoustical (ultrasound), or laser energy. Microwave ablation devices utilize a microwave antenna which is inserted into a natural body opening through a duct to the zone of treatment. Microwave energy is then radiated from the antenna through the duct wall into the target tissue, often causing severe trauma to the duct wall. Consequently, many microwave ablation devices use a cooling system to help reduce this trauma. However, the cooling system complicates the device and requires that the device be sufficiently large to accommodate the cooling system. Laser ablation devices deliver laser energy to the target tissue by "burning through" the duct wall of the urethra. Healthy cells of the duct wall and healthy tissue between the target tissue and the duct wall are also indiscriminately destroyed in the process.